1. Field of the Invention
The present invention relates to a light-emitting diode (LED) device and a method for fabricating the same, and in particular it relates to a vertical LED device and a method for fabricating the same.
2. Description of the Related Art
Light-emitting diodes (LEDs) have two configurations. The LED that has electrodes arranged on the same side of an LED chip is called a horizontal LED. The LED that has electrodes arranged on the opposite sides of an LED chip is called a vertical LED. A current path flowing in and out of a semiconductor light-emitting layer of the horizontal LED needs to be turned in a direction horizontal to the LED chip. A current path can flow in and out of a semiconductor light-emitting layer of the vertical LED without turning in different directions.
The horizontal LED has disadvantages of hot spots and non-uniform current density due to the turned current path, so that the area of the horizontal LED is hard to be increased. In comparison, the vertical LED does not have over-heat portions (hot spots) or dark portions due to the uniform current density. Therefore, the area of the vertical LED could be increased. The LED chip of the LED device usually grows on a substrate wafer by an epitaxial growth method. In fabrication processes for LED devices, however, the substrate wafer needs to be cut to fabricate the individual LED chips for epitaxial layers to grow on. The loss due to the substrate wafer sawing process is high when the LED chips have a small area, and this leads to the total light-emitting area of the substrate wafer to be reduced. Also, a portion of the light-emitting layer of the horizontal LED is used for an electrode formed thereon. Therefore, the fabrication cost per light-emitting area of the vertical LED is lower than that of the horizontal LED. The vertical LEDs are usually designed as high-illumination LEDs. Additionally, the vertical LEDs have a current flow from top to bottom, which is different from a current flow in the horizontal LED. The spreading area of the current flowing in the vertical LEDs is larger and more uniform that the horizontal LED. Further, a sapphire carrier lift-off process, is required to be adopted in the conventional fabrication processes of the LED device. The sapphire carrier removal process is too complex to control the fabrication cost and yield.
Thus, a novel LED device and a method for fabricating the same are desired.